In the wake of two tyre failures which hit champion and fastest man Sebastian Vettel and rival Fernando Alonso during Friday afternoon's second free practice session, the drivers requested action.

They made their feelings clear during the routine pre-race drivers' briefing with the ruling body, the International Motoring Federation (FIA).

The FIA's F1 Race Director Charlie Whiting was asked during the meeting to look in detail at the Pirelli tyres for this weekend and to ask the Italian company to guarantee that there are no structural problems.

The drivers are more concerned than usual not only because of the two blowouts already, but also because Spa-Francorchamps is a traditional high-speed circuit with many of the characteristics of Silverstone where five drivers suffered spectacular tyre failures during the British Grand Prix on June 30.

Pirelli said that both of Friday's punctures to the right rear wheels of Vettel's Red Bull and Alonso's Ferrari were caused by debris.

One driver, who was not named, said that there was "serious concern." The driver said: "We've left it in Charlie's hands... We have to trust him."

Pirelli chief Paul Hembery said: "It is a worry for the sport because we have to go out and find what it is. There is not a lot we can do, but we will try our very best to identify it to give us an indication of what is causing it."

Pirelli plan an investigation of the circuit to try and explain the two tyre failures on Friday. Red Bull driver Mark Webber said: "We need answers – and 'debris' is not the answer."

The incident raised the spectre of the drivers threatening to strike, as they did following the fiasco at the British Grand Prix which saw several very dangerous high-speed blowouts.